As disclosed in Japanese Patent Publication No. 23,990/1993, rear wheels of an automobile may be steered by means of an actuator such as by including an electric motor which operates in association with a steering input applied to front wheels.
A steering control system of the kind described comprises, for example, a bank of various sensors such as front wheel steer angle sensor, vehicle speed sensor, rear wheel steer angle sensor, motor speed sensor or the like; an actuator such as may be constituted by a combination of an electric motor and gear or gears; and an electronic control unit including a microcomputer and drivers for controlling the energization of the motor.
With a steering control system for rear wheels, it is necessary that a current of a relatively high magnitude be fed to the electric motor of the actuator, and thus it is necessary to use thick wires and of reduced lengths to provide a connection between the electronic control unit and the actuator since otherwise significant power loss occurs. Accordingly, it is desirable that the electronic control unit be positioned adjacent to the actuator.
However, the electronic control unit must be connected with a number of sensors such as yaw rate sensor, front wheel steer angle sensor, wheel speed sensor, T/M (transmission) vehicle speed sensor or the like which are disposed at locations spaced from the rear wheels. The positioning of the electronic control unit adjacent to the rear wheels results in that the wiring which is used to provide a connection between the number of sensors and the electronic control unit must be extended over increased distances, causing an increase in the quantity of wiring used and the likelihood that signals which are fed from the sensors to the electronic control unit be susceptible to the influences of electric noises.